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Study of Irrigation Scheduling Practices

in the Pacific Northwest

Sponsored by:Bonneville Power Administration,

Pacific Northwest Generating Co-Op., and

Northwest Energy Efficiency Alliance

April 5, 2005

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Project Scope & Objectives

Phase I: Survey irrigation water management and scheduling practices in the

region

Define scientific irrigation scheduling (SIS) and develop a baseline for its practice

Collect and analyze data on irrigation water use

Develop a plan for Phase II

Phase II: Measure water savings from the SIS

Develop a simplified methodology for calculating energy savings

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Project TeamProject Team

Project Funding: Bonneville Power Administration Pacific Northwest Generating Authority Northwest Energy Efficiency Alliance

Utility Sponsors: Franklin County PUD, Benton PUD # 1, Umatilla Electric Co-Op., Grant

County PUD

Technical Team: Bonneville Oregon State University Department of Bioengineering IRZ Consulting Ground Water Management Association Franklin County Conservation District

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Scope of the StudyScope of the Study

Phase I Phase II

Farm & Crop Characteristics

Irrigation Scheduling Methods

Farm Management Practices

BaselinePractices

Actual Water Use

Energy Consumption

Deemed Savings Methodology

Implications for C&RD

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Phase I Study DesignPhase I Study Design

Working Hypotheses:

1. “All growers use a certain irrigation regime.” 2. “What distinguishes these regimes is the basis on which irrigation decisions

are made and the intensity with which this information is applied.”

Corollary Assumptions:

1. “A good irrigation practice means knowing how much water to apply and when to do it.”

2. ” A well-managed irrigation regime can save water and, hence, pumping energy use.”

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Phase I Scope & Methods

Study Period: Data Collection: January – March 2003

Final Report: December 2003

Sample Size: Surveyed 776 growers in three states (ID, OR, WA); 11 irrigation sub-

regions; 13 PUDs (75%); 3 IOUs (25%)

Data Elements: Basic Farm Characteristics

Irrigation System

Irrigation Water Management Practices

Demographics

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Scientific Irrigation Scientific Irrigation Scheduling: DefinitionScheduling: Definition

Scientific irrigation scheduling generally refers to the practice of meeting crop moisture requirements by supplying the right amount of water at the right time based on measurement of actual soil moisture and evapotranspiration (ET).

Criteria for SIS:

1. Knowledge of crop ET2. Appropriate measurement of soil moisture of crop water status3. Measurement and monitoring of actual amounts of applied

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Scientific Irrigation Scientific Irrigation Scheduling: CriteriaScheduling: Criteria

Practice Level

Use Scheduling Services

Measure Soil Moisture or Plant Water

StatusUse ET

Measure Applied Water

I Yes

Yes Yes Yes

II

Yes Yes

Yes Yes

III

Yes

Yes

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Summary of Phase I Summary of Phase I FindingsFindings

General Characteristics: Alfalfa is the prominent crop (31% of irrigated acres), followed by wheat

(17%), vegetables (10%), corn (15%), and potatoes (7%).

94% of farms use pressurized pump systems.

Local utilities are the main source of power; 4% report using on-site generation.

On-line services, primarily AgriMet, are the most commonly used sources for ET and account for 45 percent of cases.

Sprinklers are the common irrigation system (82%); gravity systems (15%); micro-irrigation, sub-surface irrigation (3%).

Irrigation districts (44%), groundwater (29%), surface water (24%) are the main sources of irrigation water recaptured tail water, wastewater, and other sources account for the remaining 5%.

Irrigation Scheduling Practices: Nearly 80 percent of farms do not use irrigation water management and only

11% use irrigation practices that meet this study’s definition of SIS.

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Summary of Phase I Summary of Phase I ResultsResults

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Summary of Phase I Summary of Phase I FindingsFindings

Scheduling Practices: Nearly 80 percent of farms do not use irrigation water management and only

11% use irrigation practices that meet this study’s definition of SIS.

Practice Level Farms Percent Irrigated Acres Percent

I 90 12% 155,175 32%

II 75 10% 52,339 11%

III 611 79% 274,270 57%

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Phase II Scope & MethodsStudy Period: Data Collection: 2004 Irrigation Season (March – October 2003)

Final Report: March 2005

Sample Size: 44 fields (22 treatment and 22 control) farms in the Benton, Franklin, Morrow and

Umatilla counties

5 fields were dropped due to equipment failure/malfunction

Data Elements: General farm and field characteristics

Irrigation system specifications

15-minute pump system status readings (using pressure gages and data loggers)

Soil water content (regular neutron probe readings)

Flow measurements (ultrasonic flow readings)

Evapotranspiration (AgriMet)

Precipitation (NOAA)

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Phase II Study DesignPhase II Study Design

Study GroupW

ater

App

licat

ion

Idea

lA

ctua

lControlTreatment

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Calculation of Water Calculation of Water SavingsSavings

Water savings from SIS are derived by comparing the difference between Actual Water Use (AW), based on field measurements, and irrigation requirements, Ideal Water Use (IW), across the two groups, that is:

Water Savings = (AWTreatment – IWTreatment) - (AWControl – IWControl)

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Calculation of Ideal Water Calculation of Ideal Water RequirementsRequirements

0 applS

SEffS

C EIRGrossSMRET

Where:

• ΣGross IRS is the gross seasonal water requirement

• ΣETc is the cumulative seasonal crop consumptive use of water

• REff is the effective rainfall during that period

• ΔSMS is the change in soil water storage during the season (the storage at end of season less the antecedent moisture)

• Eappl is the application efficiency, the proportion of water delivered to the field that is effectively stored in the root zone for use by the crop

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The Water Balance The Water Balance ModelModel

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Calculation of Energy Calculation of Energy SavingsSavings

Where:

• TDH = total dynamic head (pumping lift, pressure and head loss)

• PPE = pumping plant efficiency

• PCF = a factor to convert energy use from units of force x distance to kWh

PCFPPE

TDHsavingswaterySavingsElectricit

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Energy Savings Energy Savings CalculatorCalculator

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Summary of Phase II Summary of Phase II FindingsFindings

Other Studies: Review of 11 other studied of SIS show water savings in the range of 7% to

30%.

Variations in crop types, methodology, location, study design and sample sizes make comparison difficult. Alfalfa is the prominent crop (31% of irrigated acres), followed by wheat (17%), vegetables (10%), corn (15%), and potatoes (7%).

Phase II Results: Water savings are approximately 10%

Energy Savings are approximately 13.1%

Caveats: The results are on the conservative side given the location of the study.

Water management techniques used by the treatment group were more rigorous than normal SIS practices.